2-Aryl-3-hydroxy-4-substituted carbonyl thiophene compounds are compounds useful, for example, as intermediates for synthesis of thrombopoietin receptor activators (e.g. Patent Document 1).
As a process for producing a 2-aryl-3-hydroxy-4-substituted carbonyl thiophene compound, only a process of synthesizing a 2-aryl-3-hydroxy-4-ester thiophene compound by a known production process (e.g. Patent Document 2), and converting the ester group at the 4-position to an alkylcarbonyl group has been known (e.g. Patent Document 1). However, conversion of the ester group to an alkylcarbonyl group requires multiple steps, and thus a production process with a smaller number of steps has been desired.
As a production process which seems to be applicable to production of a 2-aryl-3-hydroxy-4-substituted carbonyl thiophene compound, a process for producing a 2-methylcarbonyl-3-hydroxy-4-substituted carbonyl thiophene compound, the 2-position of which is substituted with methylcarbonyl not with aryl (Non-Patent Document 1), a process for producing a 3-hydroxy-4-methylcarbonyl thiophene compound, the 2-position of which is unsubstituted, not substituted with aryl, or the like may be conceivable. However, these Non-Patent Documents failed to disclose a process for producing a 2-aryl-3-hydroxy-4-substituted carbonyl thiophene compound.
Patent Document 1: WO2004/108683
Patent Document 2: JP-A-48-26755
Non-Patent Document 1: J. CHEM. RESEARCH(S), 12, 386, 1985
Non-Patent Document 2: J. CHEM. RESEARCH (M), 4135, 1985